KR101243126B1 - Apparatus for detecting defects of strip edge by using visible ray and thereof detecting method - Google Patents

Abstract

The present invention relates to an apparatus and method for detecting edge defects of a steel sheet using visible light, comprising: an image photographing unit for inspecting the full width of the steel sheet by irradiating the steel sheet with visible light; A defect detection unit connected to the image photographing unit by a cable and processing an image photographed by the image photographing unit by an image processing technique to detect edge defects of the steel sheet; Provide an edge defect detection device,
The method may further include photographing an image of the steel sheet with a visible light camera in synchronization with an external trigger; Detecting an end of a width direction of the steel sheet, calculating a threshold value for intensity information of pixels used in a subordinated task, and then moving and averaging the photographed steel sheet image to a fixed position; Comprising the step of calculating the deviation between the current image and the averaged image per pixel, and binarizing the deviation to the threshold value to analyze the defect of the steel sheet using a visible light edge defect detection method to provide.
According to the present invention, by detecting the edge defects of the steel sheet using visible light, it is possible to accurately detect the occurrence and position of the edge defects of the steel sheet, the user can fully verify the edge defects of the steel sheet such as cracks, bursts, etc. Therefore, there is an effect that the measurement error of the defect detection of the steel sheet can be prevented, and the increase in the manufacturing cost due to the loss cost caused thereby can be prevented.

Description

Apparatus and method for detecting edge defects of steel sheet using visible light {APPARATUS FOR DETECTING DEFECTS OF STRIP EDGE BY USING VISIBLE RAY AND THEREOF DETECTING METHOD}

The present invention relates to a method for detecting surface defects of a steel sheet, and more particularly, by detecting edge defects of a steel sheet using visible light, the user can fully verify the visible light, which can minimize measurement errors in defect detection. The defect detection apparatus of the steel plate edge using this, and its detection method.

Recently, as the demand for high quality products of customers increases, the demand for accuracy in detecting surface defects of steel sheets also increases. Accordingly, various techniques have been proposed for detecting and verifying surface defects of steel sheets, particularly cracks and bursts, such as cracks and bursts, by inspecting the surface of steel sheets manufactured through a rolling process or a twin roll type sheet casting process.

In this conventional method, Korean Patent Publication No. 10-0509894 for a lighting apparatus for detecting surface defects of a steel sheet by photographing a camera, which is a light receiving element, using light of a specific frequency (ultraviolet rays, etc.) that does not exist in everyday life. "An apparatus for detecting surface defects of a steel sheet using a color CCD camera and multi-wavelength light and a method thereof", and the Korean Patent Application Publication No. 2010-0076838 of Korean Patent Application Publication No. Defect inspection method and apparatus of a thin steel sheet, and a method of detecting surface defects of a steel sheet such as a stainless steel material having low surface roughness and high diffused reflection using a camera information amplifier, according to Korean Patent Publication No. 10-0758460 And "Method for Detecting Surface Defects in Stainless Steel Sheet".

However, since No. 10-0509894 has a structure in which a camera receives a reflected light source by irradiating a light source in a wavelength range such as ultraviolet light instead of visible light, the image taken by the camera is very different from the image observed by the human eye. Since it appears differently, it is impossible to verify the accuracy of the detection device based on this, and in the case of 2010-0076838 and 10-758460, the user cannot directly verify the defect of the steel sheet edge detected by the detection device. Because of the structure, there is a problem that it is impossible to determine the reliability of the detection apparatus.

The present invention has been made to solve the above problems, by detecting the edge defects of the steel sheet using visible light, it is possible to accurately detect the occurrence and location of the edge defects of the steel sheet, the edge of the steel sheet such as cracks, bursts Since the defect can be fully verified by the user, an edge defect detection device of the steel sheet using visible light and its detection which can prevent the measurement error of the defect detection of the steel sheet and thereby prevent the rise of the manufacturing cost due to the loss cost. The purpose is to provide a method.

The present invention is an image taking unit for inspecting the full width of the steel sheet by irradiating visible light to the steel sheet; A defect detection unit connected to the image photographing unit by a cable and processing an image photographed by the image photographing unit by an image processing technique to detect edge defects of the steel sheet; An edge defect detection apparatus is provided.

In this case, the image capturing unit may include left and right visible light cameras for inspecting the full width of the steel sheet, and a light emitting diode block for irradiating visible light to an area including the flaw detection area of the visible light camera. .

In addition, the defect detection unit is characterized by including a left and right edge defect detection computer and an edge defect management computer for processing a management database.

In addition, there is a feature in that a converter is provided between the image capturing unit and the defect detecting unit to reduce the influence of transmission noise.

The method may further include photographing an image of the steel sheet with a visible light camera in synchronization with an external trigger; An edge detection step of detecting an end of the width direction of the steel sheet and calculating a threshold value for intensity information of pixels used in a subordinate task; Shifting the taken image of the steel sheet to a fixed position; An averaging step of averaging the photographed image over time to generate a reference image; Calculating the deviation of the shifted current image and the averaged image per pixel, and binarizing the deviation to the threshold to analyze defects in the steel sheet. Provide a method.

Here, the steel sheet image photographing step is characterized in that the memory allocation and storage in the form of a packet by adding the operation information tag to the image of the photographed steel sheet.

In addition, when a defect exists in the steel sheet, analyzing the information on the defect region of the steel sheet, analyzing the information on the defect region, and then determining the defect by using known fuzzy information; There is also a feature in that it further comprises the step of storing information relating to the said defect.

In addition, there is a characteristic in that the parallel signal processing is performed by assigning each of the above steps to each of the multiple CPUs.

According to the present invention, by detecting the edge defects of the steel sheet using visible light, it is possible to accurately detect the occurrence and position of the edge defects of the steel sheet, the user can fully verify the edge defects of the steel sheet such as cracks, bursts, etc. Therefore, there is an effect that the measurement error of the defect detection of the steel sheet can be prevented, and the increase in the manufacturing cost due to the loss cost caused thereby can be prevented.

1 is a block diagram of an edge defect detection apparatus according to the present invention.
2 is a graph showing the optical characteristics of the camera and the light emitting diode used in the edge defect detection device of the present invention, (a) is a graph showing the frequency response characteristics of the camera, (b) is a graph showing the degree of brightness of the light emitting diode .
3 is a flow chart of an edge defect detection method according to the present invention.
4 is a schedule diagram showing that each step of the edge defect detection method according to the present invention is processed in parallel by each central processing unit.
5 is an image of steel sheet edge defects detected by the edge defect detection apparatus and method according to the present invention, (a) is a steel sheet edge defect image detected on the left side, (b) is a steel sheet edge defect image detected on the right side.

Hereinafter, an apparatus for detecting edge defects of a steel sheet using visible light according to the present invention will be described in detail with reference to the accompanying drawings.

The apparatus for detecting edge defects of a steel sheet according to the present invention includes an image capturing unit and a defect detecting unit. The image capturing unit irradiates visible steel to the steel sheet to detect the full width of the steel sheet, and the defect detecting unit captures the image. Connected with a cable and a part, the image photographed by the image capturing unit is processed by an image processing technique to detect edge defects of the steel sheet.

In this case, as shown in FIG. 1, the image capturing unit observes left and right visible light cameras 4 and 5 and the left and right visible light cameras 4 and 5, which detect the full width of the steel plate 15. It includes a light emitting diode block 6 for irradiating visible light to the area including the region (17).

In this way, two cameras of the left and right visible light cameras 4 and 5 are provided to detect the full width of the steel plate, and light emission having a light source of visible light in order to obtain a clear image from the camera photographing the steel plate 15. Diode block 6 is provided. As shown in Fig. 1, the light emitting diode block 6 has a visible light source, and focuses on the irradiation area 16 of the light emitting diode block to irradiate the visible light onto the surface of the steel sheet. The irradiated area comprises the viewing area 17 of the camera.

The defect detection unit includes left and right edge defect detection computers 1 and 2 and an edge defect management computer 3 for processing a management database. This two-edge computer for detecting edge defects requires a large number of image processing tasks to be repeatedly performed within a short time. Since the image processing process is performed at a high resolution of 4 mm ² , the work time is increased exponentially and high quality images are obtained. This is because there may be a problem that can not be processed in real time.

At this time, the left and right edge defect detection computers 1 and 2 and the edge defect management computer 3 share the combined information via the asynchronous communication network 14.

Then, since the left and right visible light cameras 4 and 5 and the left and right edge defect detection computers 1 and 2 are remotely separated, the converter 7 for remote signal transmission is used to reduce the influence of transmission noise. It is installed between them, and connects each via a camera signal transmission cable 10 and an optical cable 11.

Further, the signal of the camera synchronization external trigger 8 is connected to the left and right edge defect detection computers 1, 2 through the external trigger transmission cable 12, and the left and right visible light cameras 4, 5 are connected. The time to image the steel plate 15 is synchronized.

In addition, since the edge defects of the steel sheet must be managed together with the information of the process, the steel sheet maker main computer 9 and the edge defect management computer 3 share the steel sheet manufacturing process and operation information through the synchronous communication network 13. Share.

On the other hand, as shown in Fig. 2 (a), since the visible light camera has a central response characteristic at a wavelength of 700nm, it can be seen that it reacts most sensitively to visible light, as shown in Fig. 2 (b) Likewise, it can be confirmed that the LED block 6 is installed to be uniformly irradiated over the entire width in the two-dimensional area of the steel sheet.

Hereinafter, an edge defect detection method of a steel sheet using visible light according to the present invention will be described in detail with reference to the accompanying drawings.

In the edge defect detection method of the steel sheet according to the present invention, as shown in FIG. 3, first, an image of the steel sheet is photographed with a visible light camera in synchronization with an external trigger. That is, there is a grab task for capturing an image of a steel plate in synchronization with the external trigger 8, and in the grab task, a packet in which an operation information tag received by a communication task operating at about 2 Hz is added to the captured image. Allocate and store memory in a (packet) format so that you can process sequentially in subsequent tasks.

As such, when the grab task is completed, the grab tag invokes an event to perform an edge detection task to perform the edge detection step. The edge detection task detects a widthwise end of the steel sheet in order to move the position of the manufactured steel sheet to a fixed position while moving from side to side, and calculates a threshold value for intensity information of pixels used in a subsequent task.

When the edge detection task is completed, the edge detection task calls an event to perform a shift task to perform a shift step. Here, the photographed image of the steel sheet is moved to the fixed position in order to uniformize the steel sheet moving left and right to a fixed position.

When the shift task is completed, the shift task calls an event to perform an averaging task and a deviation and binarization task. The averaging task averages the photographed image over time to generate a reference image, and the deviation and binarization task. Calculates the deviation between the averaged image and the shifted current image per pixel and binarizes the calculated deviation per pixel to the threshold calculated by the edge detection task.

In this case, if specific information exists in the edge portion of the steel plate in the binarized image, there may be a defect. Therefore, the deviation and binarization task calls an event to perform a defect area analysis task to analyze information about the defective area of the steel plate. Follow the steps. However, do not send an event to the defect area analysis task unless there is a possibility of a join. The defect region analysis task calculates contrast information of a current image, a defect existence region, shape information of a defect existence region, and the like.

When the calculation is completed, the defect area analysis task calls an event to perform the defect determination task and performs the step of determining the defect using the known fuzzy information. That is, it is determined whether steel sheet edge defects are actually present by combining fuzzy information already known through the steel sheet manufacturing process with the current image calculated in the defect region analysis task, the contrast information of the defect present region, and the shape information of the defect present region.

When the defect determination task is completed, the defect determination task calls an event for performing a defect information storage task to store the information of the edge defect and the corresponding image to make a database, and operates on the edge defect management computer 3 to provide the user. Will be shown.

On the other hand, it takes about 0.34 seconds to continuously perform the tasks shown in FIG. 3 with one computer central processing unit. When the manufacturing speed of the steel sheet is 2.5 m / sec or less, the computer for detecting left and right edge defects 1 In order to detect the total area of the steel plate, the steel plate should be photographed at 10Hz or higher. If each edge defect detection computer takes 0.34 seconds to detect steel sheet edge defects per one shot image, each edge defect detection computer cannot detect the entire area of the steel sheet. Therefore, in the present invention, each edge defect detection computer is provided with multiple central processing units, and as shown in FIG. 4, one task is assigned to each central processing unit for eight tasks, so as to perform division of labor by performing parallel signal processing. This makes it possible to inspect the entire area of the steel sheet.

Fig. 5 is an image of steel sheet edge defects detected by the edge defect detecting apparatus and method according to the present invention. The user detects steel sheet edge defects while viewing the steel sheet edge defect images on the left and right edge defect detecting computers 1 and 2. The reliability of the device can be verified. 5 (a) shows that a crack defect is detected by the edge defect image detected on the left side, and FIG. 5 (b) shows that a burst defect is detected by the edge defect image detected on the right side.

As a result, the present invention can detect the edge defects of the steel sheet by using visible light, thereby accurately detecting the occurrence and position of the edge defects of the steel sheet, and the user can fully verify the edge defects of the steel sheet such as cracks and bursts. have.

1. Computer for detecting left edge defect 2. Computer for detecting right edge defect
3. Computer for edge defect management 4. Left side visible light camera
5. Right visible light camera 6. Light emitting diode block
7. Converter 8. External trigger
9. Steel plate maker main computer 10. Camera signal transmission cable
11. Optical cable 12. External trigger transmission cable
13. Synchronous Network 14. Asynchronous Network
15. Steel plate 16. Irradiation area of light emitting diode block
17. Viewing area of the camera

Claims (8)

An image photographing unit which photographs the current image of the steel sheet by irradiating visible light onto the steel sheet;
After the current image is moved to a fixed position, the contrast information of the current image and the defect present region, the shape information of the defect present region, and the known fuzzy information are calculated using the contrast information and the contrast information. And a defect detector for detecting edge defects of the steel sheet by determining whether steel sheet edge defects are actually present by integrating the shape information. The method of claim 1,
The image capturing unit may include left and right visible light cameras for detecting the full width of the steel sheet, and light emitting diode blocks for irradiating visible light to an area including a flaw detection area of the visible light camera. Edge defect detection device of steel sheet. The method of claim 1,
And the defect detecting unit comprises a left and right edge defect detecting computer and an edge defect management computer for processing a management database. 4. The method according to any one of claims 1 to 3,
An apparatus for detecting edge defects in a steel sheet using visible light, characterized in that a converter is provided between the image capturing unit and the defect detecting unit to reduce the influence of transmission noise. A steel sheet image photographing step of photographing a current image of the steel sheet with a visible light camera in synchronization with an external trigger;
An edge detection step of detecting an end of the width direction of the steel sheet and calculating a threshold value for intensity information of the pixel;
Shifting the current image to a fixed position for uniformity of the steel plate position moving left and right;
An averaging step of averaging the images of the steel sheets photographed over time to generate a reference image;
A deviation and binarization step of calculating a deviation between the current image and the reference image per pixel and binarizing the deviation to the threshold value;
A defect region analyzing step of calculating the current image moved to the fixed position, contrast information of the defect present region, and shape information of the defect present region;
A defect determination step of determining whether steel sheet edge defects actually exist by incorporating known fuzzy information with the contrast information and the shape information;
And detecting information about the determined defects in the edge defect detection method of the steel sheet using visible light. The method of claim 5,
The steel sheet image photographing step, the edge defect detection method of the steel sheet using visible light, characterized in that for adding the operation information tag to the image of the photographed steel sheet to allocate and store the memory in the form of a packet. delete The method according to claim 5 or 6,
A method for detecting edge defects in a steel sheet using visible light, characterized in that each step is assigned to each of the multiple CPUs and subjected to division of labor.

Images